Assessment Of Blending Local And Imported Aggregates On Properties Of Their Asphalt Concrete Mixtures

Abstract

Environmental conditions in the State of Qatar together with lack of good-quality aggregates seem to severely reduce the service lives of constructed pavements. The current practice of road construction agencies in Qatar is to utilize Marshall method of mix design to arrive at the best combination of aggregates, commonly crushed local limestone or imported Gabbro as coarse and fine aggregates and a mineral filler, and the 60/70 pen. grade bitumen. Little effort was undertaken to investigate the possibility of blending the local limestone and imported Gabbro aggregates and/or utilizing a harder bitumen grade, such as the 40/50 pen., to improve the properties of produced asphalt concrete mixtures. The main objective of this study is to assess the effect(s) of using a blend of 50 % Gabbro, 50% limestone as an aggregate on the performance of the respective bituminous concrete mixtures utilizing the 40/50 and 60/70 pen. grade asphalt cements as binders, respectively. Results of the study indicate that a better Marshall stability could be obtained by blending limestone and Gabbro aggregates. However, the 40/50 pen. concrete mixtures did not exhibit superior qualities to those of the commonly used 60/70 pen. Asphalt concrete mixtures utilizing Gabbro aggregates alone showed better mix density and were less affected by water soaking.